CCSS.Math.Content.6.RP.A.3c

Math6th GradeUnderstand ratio concepts and use ratio reasoning to solve problems.

The standard

Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent.

Common Core State Standards for Mathematics

What this standard means

Students need to connect percent to “out of 100” and use that idea to find a part, such as 25% of 48. They also need to work backward when they know the part and percent, such as 18 is 30% of what number.

Mastery means students can choose a method that fits the numbers, like a tape diagram, double number line, table, or equation. They can explain why the whole is 100%. Common trouble spots are mixing up part and whole, treating 30% as 30, and dividing when they should multiply, or the reverse.

Ways to teach it

Use 100-grid shading cards to model 10%, 25%, and 40%, then match each card to a quantity problem.
Prompt students: How can 15 be 60% of a number, and what must the whole be? Explain with a diagram.
Give three exit problems: find 35% of 80, find the whole if 12 is 20%, and identify the part in a word problem.
Use a store discount tag: A jacket is 30% off and the discount is $18, so students find the original price.

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